SOLUTION:
SHEAR FORCE DIAGRAM
FA =30 kN (same in between AC)
FC (just left of C) = 30 kN
FC (just right of C) = 20 kN
FD (just left of D) = 20 kN
FD (just right of D) = 12 kN
FB =(just left of B) = 12 kN
FB (just right of B) =0 kN
Max SF occurs at A = 30 kN (and is same in between AC)